Transmission with overdrive

ABSTRACT

A transmission with an overdrive is disclosed. It includes an input planetary gear set and an output planetary gear set wherein a first element of the input planetary gear set is connected to a drive shaft and an output element of the output planetary gear set is connected to a driven shaft. The two planetary gear sets are connected with each other through a permanent connection and through a bridging clutch.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transmission for an automotive vehicle and more particularly to a 4-speed transmission including an overdrive.

2. Description of the Prior Art

According to U.S. Pat. No. 2,725,762, a transmission using a compound planetary gear set to provide four forward speed ratios and one reverse speed ratio is known. The compound planetary gear set comprises a first sun gear, a second sun gear, a group of long planetary pinions which mesh with the first sun gear, a group of short planetary pinions which mesh with the second sun gear and a ring gear. A pinion carrier has two planetary shafts for rotatably mounting the long and short pinions. This compound planetary gear set, therefore, has four rotary elements.

The transmission comprises a drive shaft, a driven shaft and a hydraulic torque converter having an impeller connected to the drive shaft, a hollow turbine shaft connected to the turbine of the torque converter, and an intermediate shaft connected to the drive shaft.

One of the four rotary elements of the planetary gear set, that is, the ring gear, is connected permanently to the driven shaft, but the other three rotary elements thereof are not permanently connected to any of the other rotary shafts, that is, the turbine and intermediate shafts. Instead of providing the permanent connection, three clutches are associated with these three rotary elements. The sun gears are connected with the turbine shaft through clutches, respectively, and the carrier is connected with the intermediate shaft through a third clutch. Two brakes when engaged hold the first sun gear and the carrier, respectively.

If the clutches and brakes are operated in the following manner, this known transmission provides a first speed (low), a second speed (intermediate), a third speed (direct drive) and a fourth speed (overdrive).

In the first, second and third speeds, turbine power is fed to the second sun gear. The carrier is held during the first speed operation, and the first sun gear is held during the second speed operation. The third or direct drive is obtained when the third clutch is also engaged to connect the carrier with the intermediate shaft which is permanenetly connected to the drive shaft bypassing the torque converter. To obtain the fourth speed or overdrive, the clutch associated with the second sun gear is disengaged and the first sun gear is held by the associated brake with the third clutch kept engaged. During the overdrive operation, the second sun gear, together with its associated intermediate shaft, free wheels at an excessively high speed.

If a ratio (α₁) of the number of teeth of the ring gear to the number of teeth of the first sun gear is assumed to be 0.5, and a ratio (α₂) of the number of teeth of the ring gear to the number of teeth of the second sun gear is assumed to be 0.417, the rotational speed of the second sun gear can be expressed as (1+α)×N where N is the rotational speed of the drive shaft. Thus, the second sun gear free wheels at a speed approximately 2.2 times that of the drive shaft and overspeeds the driven shaft during the overdrive operation. This means that when the drive shaft rotates at 6,000 rev./min, the second sun gear rotates at 13,200 rev./min.

Therefore, this transmission tends to experience vibration and durability problems because the second sun gear rotates at an excessively high speed in overdrive.

Another known transmission disclosed in Japanese patent specification (Tokkaisho) No. 51-9092 provides four speed ratios forward and one speed ratio reverse without causing any rotary element to rotate at excessively high speed. The transmission includes three simple planetary gear sets connected in tandem.

This known transmission is disadvantageous with respect to its weight, space and cost because three planetary gear sets have to be used.

An object of the present invention is therefore to provide a transmission which provides four forward speed ratios including an overdrive and one reverse speed ratio and having only two planetary gear sets, so that it has less weight and saves space and cost, and which has no rotary element that rotates at excessively higher speeds than the drive shaft, so that it is vibration free and durable over long use.

SUMMARY OF THE INVENTION

A transmission according to the present invention comprises two planetary gear sets, each having three rotary elements, viz., an input planetary gear set and an output planetary gear set. The input planetary gear set has a first element connected to a drive shaft, while, the output planetary gear set has an output element connected to a driven shaft. The output planetary gear set has a reaction element and an input element. The transmission comprises a brake which when engaged holds the reaction element of the output planetary gear set. The input planetary gear set has a second element connected permanently to the output planetary gear set and a third element. The transmission also comprises a bridging clutch which when engaged connects the third element to the output planetary gear set. The transmission further comprises means for connecting the input element of the output planetary gear set with the drive shaft for establishing a direct drive between the drive and driven shafts upon engagement of the bridging clutch and upon disengagement of the brake and for establishing an overdrive between the drive and driven shafts upon disengagement of the bridging clutch and upon engagement of the brake.

Because the input planetary gear set and the output planetary gear set cooperate with each other by means of one permanent connection and by means of the bridging clutch which is disengaged during overdrive operation, the transmission is light in weight, compact and can be manufactured at less cost.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments of the present invention are divided into 4 major Groups for ease of explanation.

FIG. 1 is a schematic illustration of an embodiment of the invention falling within Group 1;

FIG. 1A is a table showing the engagement of the clutches and brakes asscociated with the embodiment of FIG. 1 to provide the various speed ratios;

FIG. 2 is a schematic illustration of an embodiment of the invention falling within Group 2;

FIG. 2A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 2 to provide the various speed ratios;

FIG. 3 is a first embodiment of the invention falling within Group 3;

FIG. 3A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 3 to provide the various speed ratios;

FIG. 4 is a schematic illustration of a second embodiment of the invention falling with in Group 3;

FIG. 4A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 4 to provide the various speed ratios;

FIG. 5 is a schematic illustration of a third embodiment of the invention falling within Group 3;

FIG. 5A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 5 to provide the various speed ratios;

FIG. 6 is a schematic illustration of a fourth embodiment of the invention falling within Group 3;

FIG. 6A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 6 to provide the various speed ratios;

FIG. 7 is a schematic illustration of a fifth embodiment of the invention falling within Group 3;

FIG. 7A is a table showing the engagement of the clutches and brakes associated with the engagement of FIG. 7 to provide the various speed ratios;

FIG. 8 is a schematic illustration of a first embodiment of the invention falling within Group 4;

FIG. 8A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 8 to provide the various speed ratios;

FIG. 9 is a schematic illustration of a second embodiment of the invention falling within Group 4;

FIG. 9A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 9 to provide the various speed ratios;

FIG. 10 is a schematic illustration of a third embodiment of the invention falling within Group 4;

FIG. 10A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 10 to provide the various speed ratios;

FIG. 11 is a schematic illustration of a fourth embodiment of the invention falling within Group 4;

FIG. 11A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 11 to provide the various speed ratios;

FIG. 12 is a schematic illustration of a fifth embodiment of the invention falling within Group 4;

FIG. 12A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 12 to provide the various speed ratios;

FIG. 13 is a schematic illustration of a sixth embodiment of the invention falling within Group 4;

FIG. 13A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 13 to provide the various speed ratios;

FIG. 14 is a schematic illustration of a seventh embodiment of the invention falling with Group 4;

FIG. 14A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 14;

FIG. 15 is a schematic illustration of an eighth embodiment of the invention falling within Group 4; and

FIG. 15A is a table showing the engagement of the clutches and brakes associated with the embodiment of FIG. 15A to provide the various speed ratios.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the accompanying drawings, like reference numerals are used throughout all Figures to denote like parts.

All of the embodiments illustrated in FIGS. 1 through 15 are classified into the following four groups depending upon the similarlity in structure.

Group 1 . . . FIG. 1

Group 2 . . . FIG. 2

Group 3 . . . FIGS. 3˜7

Group 4 . . . FIGS. 8˜15

The above classification has been made to facilitate understanding of the similarity between the embodiments.

Group 1 . . . A transmission falling in this Group comprises two simple planetary gear sets connected in tandem using a bridging clutch and the bridging clutch is connected to a driven shaft of the transmission.

Referring to FIG. 1, an embodiment according to Group 1 is explained.

FIG. 1 EMBODIMENT

In FIG. 1, T/C denotes a hydraulic torque converter which has a pump impeller I connected to a drive shaft A₀, a turbine runner T connected to a turbine shaft A₁, and a stator U. The transmission also comprises a planetary gear train including an output planetary gear set G₁ and an input planetary gear set G₂ and a driven shaft A₂.

Referring to the planetary gear train, the output planetary gear set G₁ includes an output element in the form of a ring gear R₁, an input element in the form of a pinion carrier PC₁ and a reaction element in the form of a sun gear S₁. The output element R₁ of the output planetary gear set is connected permanently to the driven shaft A₂. The input planetary gear set G₂ includes a first element in the form of a sun gear S₂, a second element in the form of a ring gear R₂ and a third element in the form of a pinion carrier PC₂. The first element S₂ is connected to the drive shaft A₀ through the turbine shaft A₁ and the torque converter T/C. The second element R₂ is permanently connected to the input element PC₁ of the output planetary gear set G₁, while, the third element PC₂ is connected to the output element R₁ of the output planetary gear set G₁ through a bridging clutch C₃.

The transmission comprises a direct and overdrive clutch C₁ which when engaged connects the input element PC₁ of the output planetary gear set G₁ with the drive shaft A₀ through the torque converter T/C.

An intermediate and overdrive brake B₂ of the transmission holds when engaged the reaction element S₁ of the output planetary gear set G₁.

A low and reverse brake B₁ of the transmission holds when engaged the input element PC₁ of the output planetary gear set G₁.

A reverse clutch C₂ of the transmission connects the reaction element S₁ of the output planetary gear set G₁ with the drive shaft A₀ through the torque converter T/C.

The bridging clutch C₃ connects, when engaged, the third element PC₂ not only with the output element R₁ but also with the driven shaft A₂ because the output element R₁ of the output planetary gear set G₁ is connected permanently with the driven shaft A₂.

The carrier PC₁ of the output planetary gear set G₁ rotatably mounts a plurality of pinions P₁ meshing with the ring gear R₁ and with the sun gear S₁, thus forming a simple planetary gear set.

The carrier PC₂ of the input planetary gear set G₂ rotatably mounts a plurality of pinions P₂ meshing with the ring gear R₂ and with the sun gear S₂, thus forming a simple planetary gear set.

The sequence for the engagement and release of the clutches C₁, C₂, C₃ and the brakes B₁, B₂ in the transmission of FIG. 1 is illustrated in the Table of FIG. 1A, where, α₁ denotes the ratio of the number of teeth of the ring gear R₁ to that of the sun gear S₁ and α₂ the ratio of the number of teeth of the ring gear R₂ to that of the sun gear S₂. In this example, α₁ =α₂ =0.45.

If the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the ring gear R₂ of the input planetary gear set G₂ is held by the brake B₁ and the carrier PC₂ rotates in unison with the driven shaft A₂, the power fed to the sun gear S₂ is delivered to the driven shaft A₂ through the carrier PC₂, thus rotating the driven shaft A₂ forwardly at a reduction speed. Thus, sun gear S₁ free wheels.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the carrier PC₁ rotates in unison with the ring gear R₂ and since the sun gear S₁ is held, a torque delivery path is established through the planetary gear train during intermediate speed operation.

In making a shift to the direct drive, the clutch C₁ is engaged and brake B₂ is released with clutch C₃ kept engaged. Since the power is also fed to the ring gear R₂ and the carrier PC₁, both planetary gear sets G₁ and G₂ are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratios operation, is disengaged during the fourth speed ratio or overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₁ is held and since the carrier PC₁ and ring gear R₂ are connected with the turbine shaft A₁, a torque delivery path is established through the output planetary gear set R₁. The input planetary gear set G₂ is locked and rotates in unison with the turbine shaft A₁.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all other friction elements C₁, C₃ and B₂ kept released. Since the carrier PC₁ is held, the power fed to the sun gear S₁ causes the ring gear R₁ and driven shaft A₂ to rotate backwardly. The carrier PC₂ free wheels.

In the transmission system of FIG. 1, the rotary element which rotates at the maximum speed is the ring gear R₁ during overdrive ratio operation. In this example, the ring gear R₁ rotates at a speed 1.45 times that of the turbine shaft A₁ during overdrive ratio operation.

Since the ring gear R₁ rotates in unison with the driven shaft A₂, it will be appreciated that no rotary element overspeeds the driven shaft C₃ during overdrive ratio operation.

Group 2 . . . A transmission falling in this Group is similar to the Group 1 in that it comprises two simple planetary gear sets, but different in that a bridging clutch is connected to two rotary elements which are not directly connected to a driven shaft.

FIG. 2 EMBODIMENT

Referring to FIG. 2, an embodiment according to Group 2 is explained.

In FIG. 2, a transmission comprises a planetary gear train including an output planetary gear set G₁ and an input planetary gear set G₂ and a driven shaft A₂.

Referring to the planetary gear train, the output planetary gear set G₁ includes an output element in the form of a ring gear R₁, an input element in the form of a pinion carrier PC₁ and a reaction element in the form of a sun gear S₁. The output element R₁ of the output planetary gear set G₁ is connected permanently to the driven shaft A₂. The input planetary gear set G₂ includes a first element in the form of a sun gear S₂, a second element in the form of a pinion carrier PC₂ and a third element in the form of a ring gear R₂. The first element S₂ is connected to the drive shaft A₀ through the turbine shaft A₁ and the torque converter T/C. The second element PC₂ of the output planetary gear set G₂ is permanently connected to the input element PC₁ of the output planetary gear set G₁ and thus to the driven shaft A₂, while, the third element R₂ is connected to the input element PC₁ of the output planetary gear set G₁ through a bridging clutch C₃.

The transmission comprises a direct and overdrive clutch C₁ which when engaged connects the input element PC₁ of the output planetary gear set G₁ with the drive shaft A₀ through the torque converter T/C.

An intermediate and overdrive brake B₂ of the transmission holds when engaged the reaction element S₁ of the output planetary gear set G₁.

A low and reverse brake B₁ of the transmission holds when engaged the input element PC₁ of the output planetary gear set G₁.

A reverse clutch C₂ of the transmission connects the reaction element S₁ of the output planetary gear set G₁ with the drive shaft A₀ through the torque converter T/C.

The bridging clutch C₃ holds when engaged the third element R₂ with the input element R₁ of the output planetary gear set G₁.

The carrier PC₁ of the output planetary gear set G₁ rotatably mounts a plurality of pinions P₁ meshing with the ring gear R₂ and with the sun gear S₂, thus forming a simple planetary gear set.

The carrier PC₂ of the input planetary gear set G₂ rotatably mounts a plurality of pinions P₂ meshing with the ring gear R₂ and with the sun gear S₂, thus forming a simple planetary gear set.

The sequence for the engagement and release of the clutches C₁, C₂, C₃ and the brakes B₁, B₂ in the transmission of FIG. 2 is illustrated in the Table of FIG. 2A. In this example, α₁ =α₂ =0.45

If the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the ring gear R₂ of the input planetary gear set G₂ is held, the power fed to the sun gear S₂ is delivered to the driven shaft A₂ through the carrier PC₂, thus rotating the driven shaft A₂ forwardly at a reduction speed. The carrier PC₁ and sun gear S₁ free wheel.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the ring gear R₂ rotates in unison with the carrier PC₁ and since the sun gear S₁ is held, a torque delivery path is established in the planetary gear train during intermediate ratio operation.

In making an upshift to the direct drive, the clutch C₁ is engaged and the brake B₂ is released with the clutch C₃ kept engaged. Since the power is fed also to the ring gear R₂ through the carrier PC₁ and the bridging clutch C₃, both planetary gear sets G₁ and G₂ are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratio operations, is disengaged during the fourth speed ratio and overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₁ is held and the power is fed to the pinion carrier PC₁, a torque delivery path is established through the output planetary gear set G₁. The ring gear R₂ free wheels.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all the other friction elements C₁, C₃, B₂ kept released. Since the carrier PC₁ is held, the power fed to the sun gear S₁ causes the ring gear R₁ to rotate backwardly. The ring gear R₂ free wheels.

In the transmission system of FIG. 2, the rotary element which rotates at the maximum speed is the ring gear R₂ during overdrive ratio operation. In this example, the ring gear R₂ rotates at a speed 1.65 times that of the turbine shaft A₁.

Group 3 . . . A transmission falling in this Group is similar to that of Group 1 in that a bridging clutch is connected to a driven shaft, but is different from Group 1 in that it comprises a simple planetary gear set and a dual-pinion planetary gear set.

FIG. 3 EMBODIMENT

Referring to FIG. 3, a first embodiment according to Group 3 is explained.

In FIG. 3, T/C denotes a hydraulic torque converter which has a pump impeller I to which a drive shaft A₀ is connected, a turbine runner T to which a turbine shaft A₁ is connected, and a stator U. The transmission comprises a planetary gear train including an output planetary gear set G and an input planetary gear set W and a driven shaft A₂.

Referring to the planetary gear train, the output planetary gear train G includes an output element in the form of a ring gear R₁, an input element in the form of a sun gear S₁ and a reaction element in the form of a pinion carrier PC₁. The output element R₁ of the output planetary gear set G is connected permanently to the driven shaft A₂. The input planetary gear set W includes a first element in the form of a pinion carrier PC₂, a second element in the form of a sun gear S₂ and a third element in the form of a ring gear R₂. The first element PC₂ is connected to the drive shaft A₀ through the turbine shaft A₁ and the torque converter T/C. The second element S₂ is permanently connected to the input element PC₁ of the output planetary gear set G, while, the third element R₂ is connected to the output element of the output planetary gear set G through a bridging clutch C₃ .

The transmission comprises a direct and overdrive clutch C₁ which when engaged connects the input element PC₁ of the output planetary gear set G with the drive shaft A₀ through the turbine shaft A₁ and the torque converter T/C.

An intermediate and overdrive brake B₂ of the transmission holds when engaged the reaction element S₁ of the output planetary gear set G.

A low and reverse brake B₁ of the transmission holds when engaged the input element PC₁ of the output planetary gear set G.

A reverse clutch C₂ of the transmission connects when engaged the reaction element S₁ of the output planetary gear set G with the drive shaft A₀ through the turbine shaft A₁ and the torque converter T/C.

The bridging clutch C₃ connects when engaged the third element PC₂ not only with the output element R₁ but also with the driven shaft A₂.

The carrier PC₁ of the output planetary gear set G rotatably mounts a plurality of pinions P₁ meshing with the ring gear R₁ and with the sun gear S₁, thus forming a simple planetary gear set.

The carrier PC₂ of the input planetary gear set W rotatably mounts a plurality of first pinions P₂ meshing with the ring gear R₂ and a plurality of second pinions PG₂ meshing with the sun gear S₂ and the mating first pinions P₂, thus forming a dual-pinion planetary gear set.

The sequence for the engagement and release of the clutches C₁, C₂, C₃ and the brakes B₁, B₂ in transmission of FIG. 3 is illustrated in the Table of FIG. 3A. In this example, α₁ =α₂ =0.5.

When the first gear ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the sun gear S₂ of the input planetary gear set W is held by the brake B₁ and the ring gear R₂ rotates in unison with the driven shaft A₂, the power fed to the sun gear S₂ is delivered to the driven shaft A₂ through the ring gear R₂. The sun gear S₁ free wheels.

In making a shift from the first speed ratio to the second speed ratio or intemediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the carrier PC₁ rotates in unison with the sun gear S₂ and since the sun gear S₁ is held, a torque delivery path is established through the planetary gear train during the intermediate speed operation.

In making a shift to the direct drive, the brake B₂ is released and the clutch C₁ is engaged with the clutch C₃ kept engaged. Since the power is fed also to the sun gear S₂, both planetary gear sets G and W are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratios operation, is disengaged during the fourth speed ratio or overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₁ is held and since the carrier PC₁ is connected with the turbine shaft A₁, a torque delivery path is established through the output planetary gear set G. The input planetary gear set W is locked and rotates in unison with the turbine shaft A₁.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and the low and reverse brake B₁ is applied with all other friction elements C₁, C₃ and B₂ kept released. Since the carrier PC₁ is held, the power fed to the sun gear S₁ causes the ring gear R₁ and driven shaft A₁ to rotate backwardly. The ring gear R₂ free wheels.

In the transmission system of FIG. 3, the rotary element which rotates at the maximum speed is the ring gear R₁ during overdrive ratio operation. In this example, the ring gear R₁ rotates at a speed 1.5 times that of the turbine shaft A₁ during overdrive ratio operation.

Since the ring gear R₁ rotates in unison with the driven shaft A₂, it will be appreciated that no rotary element overspeeds the driven shaft A₂ during overdrive ratio operation.

FIG. 4 EMBODIMENT

Referring to FIG. 4, a second embodiment according to Group 3 is explained.

This embodiment is substantially similar to the embodiment illustrated in FIG. 3, except that a first element of an input planetary gear set W is in the form of a sun gear S₂ and a second element thereof is in the form of a pinion carrier PC₂.

The sequence for the engagement and release of clutches C₁, C₂, C₃ and brakes B₁, B₂ in the transmission system of FIG. 4 is illustrated in the Table of FIG. 4A. In this example, α₁ =0.45 and α₂ =0.4.

When the first speed ratio or low is desired, the bridging clutch C₃ is engaged and the low and reverse brake B₁ is applied. Since the pinion carrier PC₂ of the input planetary gear set W is held and the sun gear S₂ rotates in unison with the turbine shaft A₁, a torque delivery path is established through the input planetary gear set W, thus rotating the driven shaft A₂ forwardly at a reduction speed. The sun gear S₁ of the output planetary gear set free wheels.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the carrier PC₁ rotates in unison with the carrier PC₂ and the sun gear S₁ is held, a torque delivery path is established during intermediate speed operation.

In making a shift to the third speed ratio or the direct drive, the brake B₂ is released and the direct and overdrive clutch C₁ is engaged with the bridging clutch C₃ kept engaged. Since the turbine power is also fed to the carrier PC₂, both planetary gear sets G and W are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratio operations, is disengaged during the fourth and overdrive ratio operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₁ is applied with all the other friction elements C₂, C₃, B₁ kept engaged. Since the sun gear S₁ is held and since the pinion carrier PC₁ is connected with the turbine shaft A₁, a torque delivery path is established through the output planetary gear set G. Since the turbine power is also fed to the carrier PC₂, the input planetary gear set W is locked and rotate in unison with the turbine shaft A₁.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all the other friction elements C₁, C₃ and B₂ kept released. The ring gear R₂ free wheels.

In the transmission system of FIG. 4, the rotary element which rotates at the maximum speed is the ring gear R₁ during overdrive ratio operation. In this example, the ring gear R₁ rotates 1.45 times that of the turbine shaft A₁ during overdrive ratio operation.

Since the ring gear R₁ rotates in unison with the driven shaft A₂, it will be appreciated that no rotary element overspeeds the driven shaft A₂ during overdrive ratio operation.

FIG. 5 EMBODIMENT

Referring to FIG. 5, a third embodiment of Group 3 is explained.

This embodiment is substantially the same as the embodiment illustrated in FIG. 3 in its interconnecting relationships, but is different therefrom in that a pinion carrier PC₂ of an input planetary gear set W is connected on one side to a pinion carrier PC₁ of an output planetary gear set G and connected on the opposite to a friction element of a direct and overdrive clutch C₁ which is connected to a turbine shaft at a portion rearwardly of a junction between a sun gear S₂ and the turbine shaft A₁.

The sequence for the engagement and release of clutches C₁, C₂, C₃ and brakes B₁, B₂ in the transmission of FIG. 5 is illustrated in the Table of FIG. 5A. In this example, α₁ =α₂ =0.45.

A torque delivery path established in each speed ratio is the same as that of the transmission system illustrated in FIG. 3.

In the transmission system of FIG. 5, the rotary element which rotates at the maximum speed is the ring gear R₁ during overdrive ratio operation. In this example, the ring gear R₁ rotates at a speed 1.45 times that of the turbine shaft A₁.

It will be appreciated that in the transmission system of FIG. 5, there is no rotary element which overspeeds the driven shaft A₂ during overdrive ratio operation.

FIG. 6 EMBODIMENT

Referring to FIG. 6, a fourth embodiment of Group 3 is explained.

This embodiment is substantially similar to the embodiment illustrated in FIG. 5, except that a direct and overdrive clutch C₁ is connected to a drive shaft A₀ rather than a turbine shaft A₁ to connect when engaged a carrier PC₂ with the drive shaft A₀, bypassing a torque converter T/C.

The sequence for the engagement and release of clutches C₁, C₂, C₃ and brakes B₁, B₂ in the transmission of FIG. 6 is illustrated in the Table of FIG. 6A. In this example, α₁ =α₂ =0.45.

Since the direct and overdrive clutch C₁ is released during first, second and reverse speed ratio operations, a torque delivery path in each of these speed ratio operations is the same as that of the transmission FIG. 5 or FIG. 4.

During a third speed operation when the clutch C₁ and bridging clutch C₃ are engaged with all the other friction elements kept released, an input element in the form of a carrier PC₁ of an output planetary gear set G is connected with the driven shaft through the carrier PC₂ and bypassing the torque converter T/C. In this speed ratio, the mechanical torque transmission ratio is 55%.

The fourth speed ratio or overdrive is obtained when the clutch C₁ is engaged and brake B₂ applied with all the other friction elements kept released. Since the power is fed from the driven shaft A₀ directly to the carrier PC₁ bypassing the torque converter T/C, and sun gear S₁ is held by the brake B₂, a torque delivery path through the output planetary gear set G is established. The mechanical torque transmission ratio then is 100%. The ring gear R₂ free wheels.

In the transmission system of FIG. 6, the rotary element which rotates at the maximum speed is the ring gear R₁ during overdrive ratio operation. In this example, the ring gear R₁ rotates at a speed 1.45 times that of the drive shaft A₀.

Since the ring gear R₁ rotates in unison with the driven shaft A₂, it will be appreciated that there is no rotary element which overspeeds the driven shaft A₂ during overdrive ratio operation.

FIG. 7 EMBODIMENT

Referring to FIG. 7, a fifth embodiment of Group 3 is explained.

In FIG. 7, a planetary gear train comprises an output planetary gear set W and an input planetary gear set G. The output planetary gear set W includes an output element in the form of a sun gear S₂, an input element in the form of a ring gear R₂ and a reaction element in the form of a carrier PC₂. The output element S₂ of the output planetary gear set W is connected permenently to the driven shaft A₂. The input planetary gear set G includes a first element in the form of a ring gear R₁, a second element in the form of a sun gear S₁ and a third element in the form of a pinion carrier PC₁. The first element R₁ is connected to a drive shaft A₀ through the turbine shaft A₁ and the hydraulic torque converter T/C. The second element S₁ is permanently connected to the reaction element PC₂ of the output planetary gear set W, while, the third element PC₁ is connected to the output element S₂ of the output planetary gear set W through a bridging clutch C₃.

The transmission comprises a direct and overdrive clutch C₁ which when engaged connects the input element R₂ of the output planetary gear set W with the drive shaft A₀ through the turbine shaft A₁ and torque converter T/C.

An intermediate and overdrive brake B₁ of the transmission holds when engaged the reaction element PC₂ of the output planetary gear set W.

A low and reverse brake B₁ of the transmission holds when engaged the input element R₂ of the output planetary gear set W.

A reverse clutch C₂ of the transmission connects when engaged the reaction element PC₂ of the output planetary gear set W with the drive shaft A₀ through the turbine shaft A₁ and the torque converter T/C.

The bridging clutch C₃ connects when engaged the third element PC₁ not only with the output element S₂ but also with the driven shaft A₂.

The carrier PC₂ of the output planetary gear set W rotatably mounts a plurality of first pinions P₂ on shafts PP₂ meshing with the ring gear R₂, and a plurality of second pinions PG₂ meshing with the sun gear S₂ and with the mating first pinion P₂, thus forming a dual-pinion planetary gear set.

The carrier PC₁ of the input planetary gear set G rotatably mounts a plurality of pinions P₁ meshing with the ring gear R₁ and with the sun gear S₁, thus forming a simple planetary gear set G.

The sequence for the engagement and release of clutches C₁, C₂, C₃ and brakes B₁, B₂ in the transmission of FIG. 7 is illustrated in the Table of FIG. 7A. In this example, α₁ =0.5 and α₂ =0.7.

When the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the sun gear S₁ rotates in unison with the carrier PC₂ and since the ring gear R₂ is held, a torque delivery path is established through the planetary gear train during the first speed ratio.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the carrier PC₁ is held, a torque delivery path is established through the input planetary gear set G. The ring gear R₂ free wheels.

In making a shift to the third speed ratio or direct drive, the brake B₂ is released and the clutch C₃ kept engaged. Since the power is fed to the ring gear R₂ and also to the ring gear R₁ and since the carrier PC₁ and sun gear S₁ rotate in unison with the sun gear S₂ and with the carrier PC₂, both of the output and input planetary gear sets G and W are locked and rotate in unison with the turbine shaft A₁.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratio operations, is disengaged during the fourth speed ratio or overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and the brake B₂ is applied with the other friction elements kept released. Since the carrier PC₂ is held and ring gear R₁ is connected with the turbine shaft A₁, a torque delivery path is established through the output planetary gear set W. The carrier PC₁ free wheels.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all other friction elements kept released. Since the ring gear R₂ is held and the carrier PC₂ is connected with the turbine shaft A₁, a torque delivery path is established through the output planetary gear set W, thus rotating the driven shaft A₂ backwardly.

In the transmission system of FIG. 7, the rotary element which rotates at the maximum speed is the sun gear S₂ during overdrive ratio operation. In this example, the sun gear S₂ rotates at a speed 1.43 times that of the turbine shaft A₁.

Since the sun gear S₂ rotates in unison with the driven shaft A₂, it will be appreciated that no rotary element overspeeds the driven shaft A₂ during overdrive ratio operation.

Group 4 . . . A transmission falling in the Group is similar to that of Group 1 in that a bridging clutch is connected between two rotary elements which are not a driven shaft, but is different from Group 1 in that it comprises a simple planetary gear set and a dual-pinion planetary gear set.

FIG. 8 EMBODIMENT

Referring to FIG. 8, a first embodiment according to Group 4 is explained.

In FIG. 8, T/C denotes a hydraulic torque converter which has a pump impeller I to which a drive shaft A₀ is connected, a turbine runner T to which a turbine shaft A₁ is connected and a stator U. The transmission comprises a planetary gear train including an output planetary gear set G and an input planetary gear set W and a driven shaft A₂.

Referring to the planetary gear train, the output planetary gear set includes an output element in the form of a ring gear R₁, an input element in the form of a sun gear S₁ and a reaction element in the form of a pinion carrier PC₁. The output element R₁ of the output palnetary gear set G is connected permanently to the driven shaft A₂. The input planetary gear set W includes a first element in the form of a pinion carrier PC₂, a second element in the form of a ring gear R₂ and a third element in the form of a sun gear S₂. The first element PC₂ is connected to the drive shaft A₀ through the turbine shaft A₁ and the torque converter T/C. The second element R₂ is permanently connected to the input element R₁ of the output planetary gear set G, while, the third element S₂ is connected to the input element PC₁ of the output planetary gear set G through a bridging clutch C₃.

The transmission comprises a direct and overdrive clutch C₁ which when engaged connects the input element PC₁ connects when engaged the input element PC₁ of the output planetary gear set G with the drive shaft A₀ through the torque converter T/C.

An intermediate and overdrive brake B₂ of the transmission holds when engaged the reaction element S₁ of the output planetary gear set G.

A low and reverse brake B₁ of the transmission holds when engaged the input element PC₁ of the output planetary gear set G.

A reverse clutch C₂ of the transmission connects when engaged the reaction element S₁ with the drive shaft A₀ through the turbine shaft A₁ and the torque converter T/C.

The bridging clutch C₃ connects when engaged the third element S₂ with the input element PC₁ of the output planetary gear set G.

The carrier PC₁ of the output planetary gear set G rotatably mounts a plurality of pinions P₁ meshing with the ring gear R₁ and with the sun gear S₁, thus forming a simple planetary gear set.

The carrier PC₂ of the input planetary gear set W rotatably mounts a plurality of first pinions P₂ on shafts PP₂ meshing with the ring gear R₂ and a plurality of second pinions PG₂ meshing with the sun gear and with the mating first pinion, thus forming a dual-pinion planetary gear set.

The sequence for the engagement and release of the clutches C₁, C₂, C₃ and brakes B₁, B₂ in the transmission of FIG. 8 is illustrated in the Table 8A. In this example, α₁ =0.45 and α₂ =0.6

When the first gear ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the sun gear S₂ is held and the carrier PC₂ rotates in unison with the turbine shaft A₁, a torque delivery path is established through the input planetary gear set W. The sun gear S₁ free wheels.

In making a shift from the first speed to the second speed ratio or intermediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the carrier PC₁ rotates in unison with the carrier PC₂ and since the sun gear S₁ is held, a torque delivery path is established through a planetary gear train during the intermediate speed operation.

In making a shift to the direct drive, the brake B₂ is released and the clutch C₁ is engaged with the clutch C₃ kept engaged. Since the power is fed also to the sun gear S₂, both planetary gear sets G and W are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratio operations, is disengaged during the fourth speed ratio or overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₁ is held and since the carrier PC₁ is connected with the turbine shaft A₁, a torque delivery path is established through the output planetary gear set G. Since the clutch C₃ is disengaged, the sun gear S₂ free wheels.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and the brake B₁ is applied with all the other friction elements kept released. Since the carrier PC₁ is held, forward rotation of the sun gear S₁ causes the ring gear R₁ to rotate backwardly. The sun gear S₂ free wheels.

In the transmission system of FIG. 8, the rotary element which rotates at the maximum speed is the sun gear S₂ during overdrive ratio operation. In this example, the sun gear S₂ rotates at a speed 1.75 times that of the turbine shaft A₁.

FIG. 9 EMBODIMENT

Referring to FIG. 9, a second embodiment of Group 4 is explained.

This embodiment is different from the embodiment illustrated in FIG. 8 in that an input planetary gear set W has a sun gear S₂ connected to a turbine shaft A₁ and a pinion carrier PC₂ connected with a pinion carrier of an output planetary gear set G through a bridging clutch C₃ so that the sun gear S₂ is regarded as a first element, the carrier PC₂ as a third element and a ring gear R₂ as a second element.

The sequence for the engagement of clutches C₁, C₂, C₃ and brakes B₁, B₂ in transmission system of FIG. 9 is illustrated in the Table of FIG. 9A. In this example, α₁ =0.45, α₂ =0.4.

When the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the carrier PC₂ of the input planetary gear set W is held and the sun gear S₂ rotates in unison with the turbine shaft A₁, a torque delivery path is established through the input planetary gear set W. The sun gear S₁ free wheels.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the carrier PC₁ rotates in unison with the carrier PC₂ and since the sun gear S₁ is held, a torque delivery path is established through the planetary gear train during the intermediate ratio operation.

The third speed ratio or direct drive is obtained when the direct and overdrive clutch C₁ is engaged and the bridging clutch C₃ is engaged with all other friction elements C₂, B₁, B₂ kept released. Since the turbine power is fed to the carrier PC₂ also, both planetary gear sets G and W are locked and rotate in unison.

The briding clutch C₃ which has been kept engaged during the first, second and third speed ratio operations, is disengaged during the fourth or overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₁ is held and since the carrier PC₁ is connected with the turbine shaft A₁, a torque delivery path is established through the output planetary gear set G. The pinion carrier PC₂ free wheels.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all the other friction elements C₁, C₃, B₂ kept released. Since the carrier PC₁ is held, the power fed to the sun gear S₁ causes the ring gear R₁ to rotate backwardly. The carrier PC₁ free wheels.

In the transmission system of FIG. 9, the rotary element which rotates at the maximum speed is the carrier PC₁ during overdrive ratio operation. In this example, the carrier PC₂ rotates at a speed 1.75 times that of the turbine shaft A₁.

FIG. 10 EMBODIMENT

Referring to FIG. 10, a third embodiment of Group 4 is explained.

In FIG. 10, T/C denotes a hydraulic torque converter which has a pump impeller I to which a drive shaft A₀ is connected, a turbine runner T to which a turbine shaft A₁ is connected, and a stator U. The transmission comprises a planatary gear train including an output planetary gear set G in the form of a simple planetary gear set and an input planetary gear set W in the form of a dual-pinion planetary gear set, and a driven shaft A₂.

Referring to the planetary gear train, the output planetary gear set G₁ includes an output element in the form of a ring gear R₂, an input element in the form of a pinion carrier PC₁ and a reaction element in the form of a sun gear S₂. The output element R₂ of the output planetary gear set G is connected permanently to the driven shaft A₂. The input planetary gear set W includes a first element in the form of a sun gear S₁, a second element in the form of a pinion carrier PC₁ and a third element in the form of a ring gear R₁. The first element S₁ is connected to the drive shaft A₀ through the turbine shaft A₁ and torque converter T/C. The second element PC₁ is permanently connected to the reaction element S₂ of the output planetary gear set G, while, the third element R₁ is connected to the input element PC₂ of the output planetary gear set G through a bridging clutch C₃.

The transmission comprises a direct and overdrive clutch C₁ which when engaged connects the input element PC₂ of the output planetary gear set G with the drive shaft A₀ through the torque converter T/C.

An intermediate and overdrive brake B₂ of the transmission holds when engaged the reaction element S₂ of the output planetary gear set G.

A low and reverse brake B₁ of the transmission holds when engaged the input element PC₂ of the output planetary gear set G.

A reverse clutch C₂ conects the reaction element S₂ of the output planetary gear set G with the drive shaft A₀ through the torque converter T/C.

The bridging clutch C₃ connects when engaged the third element R₁ of the input planetary gear set W with the input element PC₂ of the output planetary gear set G.

The sequence for the engagement and release of the clutches C₁, C₂, C₃ and brakes B₁, B₂ in the transmission of FIG. 10 is illustrated in the Table of FIG. 10A. In this example, α₁ =α₂ =0.45.

When the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the pinion carrier PC₂ and ring gear R₁ are held and since the carrier PC₁ rotates in unison with the sun gear S₂, a torque delivery path is established through the planetary gear train.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the pinion carrier PC₁ and sun gear S₂ are held and since the ring gear R₁ rotates in unison with the carrier PC₂, a torque delivery path is established.

In making a shift to the third speed ratio or direct drive, the direct and overdrive clutch C₁ is engaged and brake B₂ is released with clutch C₃ kept engaged. Since the power is fed also to the ring gear R₁ through the clutches C₁ and C₃, both planetary gear sets are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratio operations, is disengaged during the fourth speed ratio or overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₂ is held and since power is fed to the carrier PC₂, a torque delivery path is established through the output planetary gear set G. The ring gear R₁ free wheels.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all the other friction elements C₁, C₃, B₂ kept released. Since the power is fed to the sun gear S₂ and since the pinion carrier PC₂ is held, the driven shaft A₂ rotates backwardly. The ring gear R₁ free wheels.

In the transmission system of FIG. 10, the rotary element which rotates at the maximum speed is the ring gear R₂ during overdrive ratio operation. In this example, the ring gear R₂ rotates at a speed 1.45 times that of thr turbine shaft A₁ during the overdrive ratio operation.

Since the ring gear R₂ rotates in unison with the driven shaft A₂, it will be appreciated that there is no rotary element which overspeeds the driven shaft A₂ during overdrive ratio operation.

FIG. 11 EMBODIMENT

Referring to FIG. 11, a fourth embodiment of the Group 4 is explained.

This embodiment is different from the embodiment of FIG. 10 in that an input planetary gear set W in the form of a dual-pinion planetary gear set has a pinion carrier PC₁ connected permanently to a turbine shaft A₁ and a sun gear S₁ connected permanently to a sun gear S₂ of an output planetary gear set G so that the carrier PC₁ is regarded as a first element and the sun gear S₁ as a second element.

The sequence for engagement and release of clutches C₁, C₂, C₃ abd brakes B₁, B₂ in the transmission of FIG. 11 is illustrated in the Table of FIG. 11A. In this example, α₁ =0.55 and α₂ =0.45.

When the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the carrier PC₂ and ring gear R₁ are held and since the sun gear S₂ rotates in unison with the sun gear S₁, a torque delivery path is established through the planetary gear train.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and the intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the sun gear S₁ and sun gear S₂ are held and since the pinion carrier PC₂ rotates in unison with the ring gear R₁, a torque delivery path is established through the planetary gear train.

In making a shift to the third or direct drive, the clucth C₃ is engaged and brake B₂ is released with the clutch C₃ kept engaged. Since the turbine power is also fed to the ring gear R₁ through the clutches C₁ and C₃, both planetary gear sets W and G are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratio operations, is disengaged during the fourth speed ratio or overdrive ratio operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₂ is held and the turbine power is fed to the carrier PC₂, a torque delivery path is established through the output planetary gear set G. The ring gear R₁ free wheels.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all other friction elements C₁, C₃, B₂ kept released. The ring gear R₁ free wheels.

In the transmission system of FIG. 11, the rotary element which rotates at the maximum speed is the ring gear R₂ during overdrive ratio operation. In this example, the ring gear R₂ rotates at a speed 1.45 times that of the turbine shaft A₁ during overdrive ratio operation.

Since the ring gear R₂ rotates in unison with the driven shaft A₂, it will be appreciated that there is no rotary element which overspeeds the driven shaft A₁ during overdrive ratio operation.

FIG. 12 EMBODIMENT

Referring to FIG. 12 a fifth embodiment of Group 4 is explained.

In FIG. 12, this embodiment is different from the embodiment of FIG. 11 in that an input planetary gear train W in the form of a dual-pinion planetary gear set has a sun gear S₂ connected to a drive shaft A₀ through a torque converter T/C, a ring gear R₂ permanently connected to an input element PC₁ of an output planetary gear set G, and a pinion carrier PC₂ connected to a reaction element S₁ of the output element G through a bridging clutch C₃.

The sequence for the engagement and release of the cluthes C₁, C₂, C₃ and brakes B₁, B₂ in the transmission of FIG. 12 is illustrated in the Table of FIG. 12A. In this example, α₁ =α₂ =0.45.

When the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the carrier PC₁ and ring gear R₂ are held and since the sun gear S₁ rotates in unison with carrier PC₂, a torque delivery path is established so that the power fed to the sun gear S₂ causes the ring gear R₁ and the driven shaft A₂ to rotate forwardly.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the sun gear S₁ and carrier PC₂ are held, a torque delivery path where two planetary gear sets are active is established.

In making a shift to the third speed ratio or direct drive, the brake B₂ is released and direct and overdrive clutch C₁ is engaged with the clutch C₃ kept engaged. Since the turbine power is fed also to ring gear R₂ and carrier PC₁, both of the planetary gear sets W and G are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratio operations, is disengaged during the fourth speed ratio or overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₁ is held, a torque delivery path is established through the output planetary gear set G. The carrier PC₂ free wheels.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all other friction elements C₁, C₃, B₂ kept released. Since the carrier PC₁ is held and power is fed to the sun gear S₁, a torque delivery path is established through the output planetary gear set G. The carrier PC₂ free wheels.

In the transmission system of FIG. 12, the rotary element which rotates at the maximum speed is the ring gear R₁ during overdrive ratio operation. In this example, the ring gear R₁ rotates at a speed 1.45 times that of the turbine shaft A₁. Since the ring gear R₁ rotates in unison with the driven shaft A₂, it will be appreciated that no rotary element overspeeds the driven shaft A₂ during overdrive ratio operation.

FIG. 13 EMBODIMENT

Referring to FIG. 13, a sixth embodiment of the Group 4 is explained.

This embodiment is different from the embodiment of FIG. 12 in that an input planetary gear set W in the form of a dual-pinion planetary gear set has a pinion carrier PC₂ connected to a drive shaft A₀ through a torque converter T/C, a ring gear R₂ permanently connected to an input element PC₁ of an output planetary gear set G, and a sun gear S₃ connected to a sun gear S₁ through a bridging clutch C₃, so that the pinion carrier PC₂ can be regarded as a first element, the ring gear R₂ as a second element, and the sun gear S₂ as a third element.

The sequence for the engagement and release of clutches C₁, C₂, C₃ and brakes B₁, B₂ in the transmission of FIG. 13 is illustrated in the Table of FIG. 13A. In this example, α₁ =0.45 and α₂ =0.55.

When the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since pinion carrier PC₁ and ring gear R₂ are held and since sun gear S₁ rotates in unison with sun gear S₂, a torque delivery path where both planetary gear sets G and W are active is established.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and brake B₂ is applied with clutch C₃ kept engaged. Since sun gear S₁ and sun gear S₂ are held and since ring gear R₂ rotates in unison with pinion carrier PC₁, a torque delivery path where both of planetary gear sets G and W are active is established.

In making a shift to the third speed ratio or direct drive, the brake B₂ is released and clutch C₁ is engaged with clutch C₃ kept engaged. Since the power is fed also to ring gear R₂, both planetary gear sets are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during first, second and third speed ratio operations, is disengaged during the fourth speed ratio or overdrive operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the sun gear S₁ is held and since PC₁ rotates in unison with the carrier, the sun gear S₁ is held and the power is fed to the pinion carrier PC₁, a torque delivery path is established through the output planetary gear set G.

The reverse speed ratio is established when the reverse clutch C₂ is engaged and the low and reverse brake B₁ is applied. Since the pinion carrier PC₂ is held and the power is fed to sun gear S₁, a torque delivery path performing the reverse drive is established.

In the transmission of FIG. 13, the rotary element which rotates at the maximum speed is the ring gear R₁ during overdrive ratio operation. In this example, the ring gear R₁ rotates at a speed 1.45 times that of the turbine shaft A₁. Since the ring gear R₁ rotates in unison with the driven shaft A₂, it will be appreciated that there is no rotary element which overspeeds the driven shaft A₂ during overspeed ratio operation.

FIG. 14 EMBODIMENT

Refering to FIG. 14, a seventh embodiment of Group 4 is explained.

This embodiment is substantially similar to the embodiment illustrated in FIG. 12 except that a direct and overdrive clutch C₁ connects when engaged a ring gear R₂ of an output planetary gear set W with a drive shaft A₀, bypassing a hydraulic torque converter T/C.

The sequence for the engagement and release of clutches C₁, C₂, C₃ and brakes B₁, B₂ in the transmission of FIG. 14 is illutrated in the Table of FIG. 14A. In this example, α₁ =α₂ =0.45.

The operation of this embodiment is however different from the embodiment in FIG. 12 during third speed ratio and fourth speed ratio operations.

The third speed ratio is obtained when clutch C₁ and clutch C₃ are engaged with all the other friction elements kept released. Since the power on the drive shaft A₀ is fed to carrier PC₁ and ring gear R₂ and the power on the turbine shaft A₁ is fed to sun gear S₂ and since the sun gear S₁ rotates in unison with carrier PC₂, a torque delivery path is established where two planetary gear sets G and W are active and where the mechanical torque transmission ratio is 63%.

The fourth speed ratio or overdrive ratio operation is obtained when a direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, B₁ kept released. Since the sun gear S₁ is held and the power on the drive shaft A₀ is fed to the carrier PC₁, a torque delivery path providing overdrive is established through the planetary gear set G. The mechanical torque transmission ratio in this overdrive is 100%.

In the transmission system of FIG. 14, the rotary element which rotates at the maximum speed is the ring gear R₁ during overdrive ratio operation. In this example, the ring gear R₁ rotates at a speed 1.45 times that of the turbine shaft A₁ during overdrive ratio operation. Since the ring gear R₁ rotates in unison with the driven shaft A₂, it will be appreciated that no rotary element overspeeds the driven shaft A₂ during the overdrive ratio operation.

FIG. 15 EMBODIMENT

Referring to FIG. 15, an eighth embodiment of the Group 4 is explained.

This embodiemnt is different from the embodiment of FIG. 13 in that an input planetary gear set in the form of a dual-pinion planetary gear set W has a ring gear R₂ connected to an output element R₁ of the output planetary gear set G and a pinion carrier PC₂ connected to an input element PC₁ of the output planetary gear set G through a direct and overdrive clutch C₁.

The sequence for the engagement and release of the clutches C₁, C₂, C₃ and brakes B₁, B₂ in the tranmission of FIG. 15 is illustrated in the Table of FIG. 15A. In this example, α₁ =0.4 and α₂ =0.55.

When the first speed ratio or low is desired, the bridging clutch C₃ is engaged and low and reverse brake B₁ is applied. Since the power on the turbine shaft A₁ is fed to the carrier PC₂ and the carrier PC₁ is held and since the sun gear S₁ rotates in unison with the sun gear S₂, a torque delivery path wherein two planetary gear sets G and W are active is established.

In making a shift from the first speed ratio to the second speed ratio or intermediate, the brake B₁ is released and intermediate and overdrive brake B₂ is applied with the clutch C₃ kept engaged. Since the turbine power is fed to the carrier PC₂ and the sun gear S₂ is held, a torque delivery path is established through the input planetary gear set W. The pinion carrier PC₁ free wheels.

The third and direct drive is established when the clutch C₁ and clutch C₃ are engaged with all the other friction elements kept released. The planetary gear sets are locked and rotate in unison.

The bridging clutch C₃ which has been kept engaged during the first, second and third speed ratios, is now disengaged during the fourth speed ratio operation. The overdrive is obtained when the direct and overdrive clutch C₁ is engaged and intermediate and overdrive brake B₂ is applied with all the other friction elements C₂, C₃, B₁ kept released. Since the power is fed to the carrier PC₁ through the clutch C₁ and since the sun gear S₁ is held, a torque delivery path providing an overdrive is established through the output planetary gear set G.

The reverse speed ratio is obtained when the reverse clutch C₂ is engaged and low and reverse brake B₁ is applied with all the other friction elements kept released. Since the carrier PC₁ is held and the power is fed to the sun gear S₁, a torque delivery path providing the reverse drive is established through the output planetary gear set G. The sun gear S₂ free wheels.

In the transmission system of FIG. 15, the rotary element which rotates at the maximum speed is the sun gear S₂ during overdrive ratio operation. In this example, the sun gear S₂ rotates at a speed 1.75 times that of turbine shaft A₁.

As having been described, according to the present invention, among the rotary elements of two planetary gear sets, only one pair of rotary elements is permanently connected, while, another pair of rotary elements are inner connected through a bridging clutch, and this clutch is released during the fourth speed ratio providing an overdrive, thus making it possible to provide an overdrive without any increase in component parts and without increase in weight, space and cost. Moreover, according to the present invention, there is no rotatry element which rotates at excessively high speed, thus providing an advantage in terms of low vibration and increased durability. Furthermore, according to FIGS. 6 and 14 embodiments, a split power drive between torque converter input (fluid drive) and a direct input (mechanical drive) is employed so that energy loss due to rotary vibration and slippage in the torque converter is reduced. 

What is claimed is:
 1. A transmission for an automotive vehicle, comprising:a drive shaft; a driven shaft; a planetary gear train between said drive and driven shafts which includes only two planetary gear sets and which comprises:an output planetary gear set having an output element connected to said driven shaft, an input element and a reaction element, a brake effective upon engagement to hold said reaction element, an input planetary gear set having a first element connected to said drive shaft, a second element, and a third element, a bridging clutch effective upon engagement to connect said third element of said input planetary gear set with said output planetary gear set, first means for establishing a first power path connecting said input element of said output planetary gear set to said drive shaft to provide a direct drive between said drive and driven shafts upon engagement of said bridging clutch and upon disengagement of said brake, said second element of said input planetary gear set being permanently connected to said output planetary gear set, and second means for establishing a second power path connecting said input element of said output planetary gear set to said drive shaft to provide an overdrive between said drive and driven shafts upon disengagement of said bridging clutch and upon engagement of said brake.
 2. A transmission as claimed in claim 1, wherein said first means for establishing said first power path comprises:a hydraulic torque converter, and a direct and overdrive clutch effective upon engagement to connect said input element of said output planetary gear set to said drive shaft through said torque converter, wherein said first element of said input planetary gear set is connected to said drive shaft through said hydraulic torque converter, and wherein said brake is effective upon engagement to hold said reaction element of said output planetary gear set for establishing an intermediate reduction gear ratio between said drive and driven shafts upon engagement of said bridging clutch and of said brake and upon disengagement of said direct and intermediate clutch.
 3. A transmission as claimed in claim 1, wherein said first means for establishing said first power path includes a hydraulic torque converter, anda direct and overdrive clutch effective upon engagement to connect said input element of said output planetary gear set with said drive shaft bypassing said hydraulic torque converter, wherein said first element of said input planetary gear set is connected to said drive shaft through said hydraulic torque converter, and wherein said brake is effective upon engagement to hold said reaction element of said output planetary gear set for establishing an intermediate reduction gear ratio between said drive and drive shafts upon engagement of said bridging clutch and of said brake and upon disengagement of said direct and overdrive clutch.
 4. A transmission as claimed in claim 2 or claim 3, wherein said planetary gear train includesa low and reverse brake effective upon engagement to hold said input element of said output planetary gear set for establishing a low reduction gear ratio upon engagement of said bridging clutch and upon disengagement of said first-mentioned brake and of said direct and overdrive clutch.
 5. A transmission as claimed in claim 4, wherein said planetary gear train includesa reverse clutch effective upon engagement to connect said reaction element of said output planetary gear set with said turbine shaft through said hydraulic torque converter for establishing a reverse drive between said drive and driven shafts upon engagement of said low and reverse brake and upon disengagement of said bridging clutch, of said direct and overdrive clutch and of said first-mentioned brake.
 6. A transmission as claimed in claim 5, wherein said output planetary gear set is a simple planetary gear set,wherein said third element of said input planetary gear set is connected through said bridging clutch to said output element of said output planetary gear set, and said second element of said input planetary gear set is connected to said input element of said output planetary gear set, whereby said input planetary gear set is locked during operation of the transmission during overdrive operation.
 7. A transmission as claimed in claim 5, wherein said output planetary gear set is a dual-pinion planetary gear set,wherein said third element of said input planetary gear set is connected through said bridging clutch to said output element of said output planetary gear set, and said second element of said input planetary gear set is connected to said reaction element.
 8. A transmission as claimed in claim 5, wherein said third element of said input planetary gear set is connected through said bridging clutch with said input element of said output planetary gear set, andsaid second element of said input planetary gear set is connected to one of said reaction element and said output element of said output planetary gear set.
 9. A transmission as claimed in claim 6, wherein said input planetary gear set is a simple planetary gear set, wherein;said input element of said output planetary gear set is a pinion carrier, said reaction element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a ring gear, and said third element of said input planetary gear set is a pinion carrier.
 10. A transmission as claimed in claim 8, wherein said output planetary gear set is a simple planetary gear set, and said input planetary gear set is a simple planetary gear set,wherein said input element of said output planetary gear set is a pinion carrier, said reaction element of said output planetary gear set is a sun gear, and said output element of said output planetary gear set is a ring gear, and wherein said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a pinion carrier, and said third element of said output planetary gear set is a ring gear, and wherein said second element of said input planetary gear set is connected to said output element of said output planetary gear set.
 11. A transmission as claimed in claim 6, wherein said input planetary gear set is a dual-pinion planetary gear set,wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, and wherein said first element is a pinion carrier, said second element is a sun gear, and said third element is a ring gear.
 12. A transmission as claimed in claim 6, wherein said input planetary gear set is a dual-pinion planetary gear set,wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a pinion carrier, wherein said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a pinion carrier, and said third element of said input planetary gear set is a ring gear.
 13. A transmission as claimed in claim 6, wherein said input planetary gear set is a dual-pinion planetary gear set,wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, wherein said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a pinion carrier, and said third element of said input planetary gear set is a ring gear.
 14. A transmission as claimed in claim 6, wherein said input planetary gear set is a dual-pinion planetary gear set,wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, wherein said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a pinion carrier, and said third element of said input planetary gear set is a ring gear.
 15. A transmission as claimed in claim 7, wherein said input planetary gear set is a simple planetary gear set,wherein said input element of said output planetary gear set is a ring gear, said output element of said output planetary gear set is a sun gear, and said reaction element of said output planetary gear set is a pinion carrier, and wherein said first element of said input plnetary gear set is a ring gear, said second element of said input planetary gear set is a sun gear, and said third element of said input planetary gear set is a pinion carrier.
 16. A transmission as claimed in claim 8, wherein said second element of said input planetary gear set is connected to said output element of said output planetary gear set,wherein said output planetary gear set is a simple planetary gear set and said input planetary gear set is a dual-pinion planetary gear set, wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, wherein said first element of said input planetary gear set is a pinion carrier, said second element of said input planetary gear is a ring gear, and said third element of said input planetary gear set is a sun gear.
 17. A transmission as claimed in claim 8, wherein said second element of said input planetary gear set is connected to said output element of said output planetary gear set,wherein said output planetary gear set is a simple planetary gear set and said input planetary gear set is a dual-pinion planetary gear set, wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, wherein said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a ring gear, and said third element of said input planetary gear set is a pinion carrier.
 18. A transmission as claimed in claim 8, wherein said second element of said input planetary gear set is connected to said reaction element of said output planetary gear set,wherein said output planetary gear set is a simple planetary gear set and said input planetary gear set is a dual-pinion planetary gear set, wherein said input element is a pinion carrier, said output element is a ring gear, and said reaction element is a sun gear, and wherein said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a pinion carrier, and said third element of said input planetary gear set is a ring gear.
 19. A transmission as claimed in claim 8, wherein said second element of said input plantary gear set is connected to said reaction element of said output planetary gear set,wherein said output planetary gear set is a simple planetary gear set and said input planetary gear set is a dual-pinion planetary gear set, wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, and wherein said first element of said input planetary gear set is a pinion carrier, said second element of said input planetary gear set is a sun gear, and said third element of said input planetary gear set is a ring gear.
 20. A transmission as claimed in claim 5, wherein said third element of said input planetary gear set is connected through said bridging clutch with said reaction element of said output planetary gear set, andsaid second element of said input planetary gear set is connected to said input element of said output planetary gear set.
 21. A transmission as claimed in claim 20, wherein said output planetary gear set is a simple planetary gear set and said input planetary gear set is a dual-pinion planetary gear set,wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, and wherein said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a ring gear, and said third element of said input planetary gear set is a pinion carrier.
 22. A transmission as claimed in claim 20, wherein said output planetary gear set is a simple planetary gear set and said input planetary gear set is a dual-pinion planetary gear set,wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, and wherein said first element of said input planetary gear set is a pinion carrier, said second element of said input planetary gear set is a ring gear, and said third element of said input planetary gear set is a sun gear.
 23. A transmission as claimed in claim 20, wherein said output planetary gear set is a simple planetary gear set and said output planetary gear set is a dual-pinion planetary gear set,and wherein said input element of said output planetary gear set is a pinion carrier, said output planetary gear set of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, and wherein said first element of said input planetary gear set is a sun gear, said second element of said input planetary gear set is a ring gear, and said third element of said input planetary gear set is a pinion carrier.
 24. A transmission as claimed in claim 5, wherein said third element of said input planetary gear set is connected through said first-mentioned clutch with said reaction element of said output planetary gear set, andsaid second element of said input planetary gear set is connected to said output element of said output planetary gear set.
 25. A transmission as claimed in claim 24, wherein said output planetary gear set is a simple planetary gear set and said input planetary gear set is a dual-pinion planetary gear set,and wherein said input element of said output planetary gear set is a pinion carrier, said output element of said output planetary gear set is a ring gear, and said reaction element of said output planetary gear set is a sun gear, and wherein said first element of said input planetary gear set is a pinion carrier, said second element of said input planetary gear set is a ring gear, and said third element of said input planetary gear set is a sun gear. 